The present invention relates to a motor controller and a steering device.
Japanese Laid-Open Patent Publication No. 2004-182039 describes an example of a vehicle steering device for vehicles. The vehicles steering device includes motors for a plurality of systems and a steering controller serving as a motor controller that controls actuation of the motors.
In detail, the steering controller controls the actuation two systems of motors, which include a first motor having a first motor winding and a second motor having a second motor winding, to apply power to a steering mechanism. The steering controller includes a first system and a second system. The first system includes a first ECU combined with a first drive circuit to supply current to the first motor, and the second system includes a second ECU combined with a second drive circuit to supply current to the second motor. Further, an external device inputs a steering angle of a steering wheel as a position signal to each of the first and the second ECUs. Independent rotation angle sensors that detect rotation angles of the first and the second motors are connected to the first and the second ECUs, respectively.
Specifically, the first ECU generates a torque instruction value by using the position signal input to the first ECU. The torque instruction value is distributed to the first ECU and the second ECU by the first ECU. Each of the first and the second ECUs controls actuation of the corresponding drive circuit based on the torque instruction value distributed to itself and a detection result of the corresponding rotation angle sensor. That is, the first ECU functions as a master, and the second ECU functions as a slave.
The second ECU is formed to interrupt the supply of current from the first system to the first motor winding when the first ECU is abnormal such as when an abnormality is included in the position signal input to the first ECU serving as the master from the external device or the detection result of the rotation angle sensor connected to the first ECU. In this case, the second ECU serving as the slave generates the torque instruction value by using the position signal input from the external device and controls the actuation of the corresponding drive circuit by using the detection result of the rotation angle sensor connected to the second ECU. That is, when the first ECU is abnormal, at least the supply of current from the second ECU to the second motor winding is maintained to ensure output of the second motor.
As described in Japanese Patent Publication No. 2004-182039, when the first ECU serving as the master is abnormal, the supply of current from the first ECU to the first motor winding is interrupted. Thus, the output of the first motor is lost. That is, the total motor output when the first ECU is abnormal is equal to one-half of total motor output when the first ECU is normal. Thus, it is desirable that the decrease in the total motor output be minimized when the first ECU serving as the master is abnormal. Such a desire is not limited to a device that supplies power to a vehicle steering mechanism and also arises when a device control actuation of a motor.